Aqueous dispersion of inorganic nanoparticles, method for the production and use thereof

ABSTRACT

An aqueous dispersion with a pH of from 2 to 7, comprising (A) at least one swellable polymer or oligomer containing anionic and/or potentially anionic functional groups, (B) surface-modified, cationically stabilized, inorganic nanoparticles of at least one kind, and (C) at least one amphiphile; and its use for producing highly scratch-resistant coatings, moldings, and self-supporting films.

FIELD OF THE INVENTION

The present invention relates to a novel aqueous dispersion of inorganicnanoparticles. The present invention also relates to a novel process forpreparing aqueous dispersions of inorganic nanoparticles. The presentinvention further relates to the use of the novel aqueous dispersion ofinorganic nanoparticles for producing coatings and paint systems andalso moldings, especially optical moldings, and self-supporting films.

STATE OF THE ART

Aqueous dispersions of inorganic nanoparticles with their surfacemodified with at least one compound of the general formula II:[(S-)_(o)-L-]_(m)(R)_(n)(H)_(p)  (II)in which the indices and variables have the following meanings:

-   S is a reactive functional group;-   L is an at least divalent organic linking group;-   H is a hydrolyzable monovalent group or a hydrolyzable atom;-   M is a divalent to hexavalent main group or transition group metal;-   R is a monovalent organic radical;-   o is an integer from 1 to 5;-   m+n+p is an integer from 2 to 6;-   p is an integer from 1 to 6, and-   m and n are zero or an integer from 1 to 5    are known from international patent application WO 99/52964. They    are prepared by coating inorganic nanoparticles with the compounds    II in aqueous dispersion, and then distillatively removing the    alcohols formed by the hydrolysis and condensation.

The known aqueous dispersions of surface-modified inorganicnanoparticles may be used as coating materials for producingtransparent, scratch-resistant coatings.

These known coatings are of high transparency and good adhesion to alarge number of substrates. However, they are comparatively brittle andcannot be produced in coat thicknesses >30 μm, since stress cracks thenoccur. Moreover, the known coatings undergo delamination comparativelyreadily following exposure to water.

European patent application EP 0 832 947 A2 discloses clearcoatmaterials comprising inorganic nanoparticles whose surface has beenmodified such that it is able to react with the binder. The scratchresistance of the clearcoats produced from these clearcoat materialsdoes not, however, match that of the coatings known from internationalpatent application WO 99/52964. Moreover, the clearcoat materials of theEuropean patent application include large amounts of organic solvents,and so give off large amounts of volatile organic compounds (VOCs) onapplication and curing, which is economically and environmentallydisadvantageous.

German patent application DE 101 26 651.0, unpublished at the prioritydate of the present specification, describes coating materials whichcomprise

-   (A) at least one binder selected from the group consisting of    random, alternating, and block, linear, branched, and comb,    polyaddition resins, polycondensation resins, and addition    (co)polymers of olefinically unsaturated monomers, curable    physically, thermally, with actinic radiation, and both thermally    and with actinic radiation; and-   (B) nanoparticles selected from the group consisting of    nanoparticles that have been modified with at least one compound of    the general formula (II):    [(S-)_(o)-L-]_(n)-M-(-X-R)_(m-n)  (II)    in which the indices and variables have the following meanings:-   S is a reactive functional group containing at least one bond which    can be activated with actinic radiation;-   L is an at least divalent organic linking group;    -   X independently at each occurrence is an oxygen atom, sulfur        atom or >NR⁶, where R⁶=hydrogen atom or alkyl group having from        1 to 4 carbon atoms;-   M is a metal atom;-   R is a monovalent organic radical;-   o is an integer from 1 to 5;-   m is 3 or 4;-   n is 1 or 2 if m=3 and-   n is 1, 2 or 3 if m=4.

The coating materials may comprise (meth)acrylate copolymers as binders.Besides numerous other monomers, the (meth)acrylate copolymers may alsocontain, in copolymerized form, monomers (b) of the general formula I:R¹R²C═CR³R⁴  (I)in which the radicals R¹, R², R³, and R⁴ each independently of oneanother are hydrogen atoms or substituted or unsubstituted alkyl,cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl,cycloalkylaryl, arylalkyl or arylcycloalkyl radicals, with the provisothat at least two of the variables R¹, R², R³, and R⁴ are substituted orunsubstituted aryl, arylalkyl or arylcycloalkyl radicals, especiallysubstituted or unsubstituted aryl radicals.

The coating materials may be conventional systems comprising organicsolvents, aqueous systems, substantially or entirely solvent- andwater-free liquid coating materials (100% systems), substantially orentirely solvent- and water-free solid coating materials (powder coatingmaterials), or substantially or entirely solvent-free powder coatingsuspensions (powder slurries). The examples, however, describe only aconventional clearcoat material comprising organic solvents. Moreover,the electrophoretic mobility of the binders in an aqueous dispersionwith a pH of from 2 to 7 is not specified.

German patent application DE 101 15 592.1, unpublished at the prioritydate of the present specification, describes aqueous dispersions whichare free or substantially free from volatile organic compounds andcomprise

-   (A) at least one copolymer preparable by two-stage or multistage    free-radical copolymerization in an aqueous medium of-   a) at least one olefinically unsaturated monomer selected from the    group consisting of hydrophilic and hydrophobic olefinically    unsaturated monomers and-   b) at least one non-(a) olefinically unsaturated monomer of the    general formula (I)    R¹R²C═CR³R⁴  (I)    in which the radicals R¹, R², R³, and R⁴ each independently of one    another are hydrogen atoms or substituted or unsubstituted alkyl,    cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl,    cycloalkylaryl, arylalkyl or arylcycloalkyl radicals, with the    proviso that at least two of the variables R¹, R², R³, and R⁴ are    substituted or unsubstituted aryl, arylalkyl or arylcycloalkyl    radicals, especially substituted or unsubstituted aryl radicals; and-   (B) hydrophilic nanoparticles.

The surface of the hydrophilic nanoparticles, however, is unmodified.

PROBLEM OF THE PRESENT INVENTION

It is an object of the present invention to provide novel aqueousdispersions of surface-modified inorganic nanoparticles which no longerhave the disadvantages of the state of the art but instead are stable onstorage and give coatings and paint systems, and also optical moldingsand self-supporting films, which are highly scratch resistant, of highgloss, flexible, transparent, and clear, the coatings and the paintsystems no longer exhibiting any stress cracks at coat thicknesses >30μm or any delamination from the substrates.

A particular object of the present invention was to provide novelaqueous dispersions which have a high nanoparticle content.

THE SOLUTION ACCORDING TO THE INVENTION

The invention accordingly provides the novel aqueous dispersion with apH of from 2 to 7, comprising

-   (A) at least one swellable polymer or oligomer containing anionic    and/or potentially anionic and/or nonionic hydrophilic groups,-   (B) surface-modified, cationically stabilized, inorganic    nanoparticles of at least one kind, and-   (C) at least one amphiphile,    and referred to below as “dispersion of the invention”.

Further subject matter of the invention will emerge from thedescription.

In the light of the state of the art it was surprising and unforeseeablefor the skilled worker that the object on which the present inventionwas based could be achieved by means of the dispersion of the invention.

Since a positive surface charge is essential for a series of aqueousdispersions of inorganic nanoparticles (examples being boehmite andcertain silica sols), it was all the more suprising that a combinationof cationically stabilized, surface-modified, inorganic nanoparticleswith anionically stabilized polymers and oligomers leads tostorage-stable aqueous dispersions. More surprising still was that thiswas achievable by means of copolymers which were readily swellable inaqueous media with a pH of from 2 to 7 and which therefore exhibitedgood electrophoretic mobility. A particular surprise was that thedispersions of the invention had a particularly high nanoparticlecontent.

DETAILED DESCRIPTION OF THE INVENTION

The dispersion of the invention has a pH of from 2 to 7, preferably from2.5 to 7 and in particular from 3 to 6.5. The pH is adjusted by addingorganic and/or inorganic acids which do not undergo any unwantedreactions with the starting products and with the constituents of thedispersion of the invention, such as precipitation reactions or thedecomposition of nanoparticles (B). Examples of suitable acids areformic, acetic, and hydrochloric acid.

The solids content of the dispersion of the invention may vary verywidely and is guided by the requirements of the case in hand. It ispreferably from 10 to 80%, more preferably from 15 to 75%, withparticular preference from 20 to 70%, with very particular preferencefrom 25 to 65%, and in particular from 30 to 60% by weight, based ineach case on the total amount of the dispersion of the invention.

The first essential constituent of the dispersion of the invention is atleast one, especially one, swellable polymer or oligomer (A),particularly a polymer (A), containing anionic and/or potentiallyanionic functional groups.

Here and below, polymers are compounds which contain on average morethan 10 monomer units in the molecule. Oligomers are compounds whichcontain on average from 2 to 15 monomer units in the molecule. Forfurther details of this, refer to Römpp Lexikon Lacke und Druckfarben,Georg Thieme Verlag, Stuttgart, New York, 1998, page 425, “oligomers”,and page 464, “polymers”.

The anionic and potentially anionic functional groups are preferablyselected from the group consisting of carboxylic, sulfonic, andphosphonic acid groups, acidic sulfuric and phosphoric ester groups, andcarboxylate, sulfonate, phosphonate, sulfate ester, and phosphate estergroups, especially carboxylic acid and carboxylate groups.

The amount of anionic and/or potentially anionic functional groups inthe polymers and oligomers (A) may vary very widely and is guided by therequirements of the case in hand, particularly by the amount of thesegroups that is necessary in order to ensure the swellability of thepolymers and oligomers (A) in aqueous media with a pH of from 2 to 7.The amount corresponds preferably to an acid number of from 5 to 70,more preferably from 6 to 60, with particular preference from 7 to 50,with very particular preference from 8 to 40, and in particular from 9to 30 mg KOH/g. Solids here and below are the sum of the constituentswhich form the coatings, optical moldings, and self-supporting filmsproduced from the dispersion of the invention.

At pH values of from 2 to 7 the swellable polymers and oligomers (A)preferably have an electrophoretic mobility ≦−0.5, more preferably ≦−2.0(μm/s)/(V/cm). The electrophoretic mobility can be determined with theaid of laser Doppler electrophoresis. The Zetasizer® 3000 from Malverncan be employed as the measuring instrument. However,microelectrophoretic (microscopic) measurement techniques are alsosuitable.

The polymers and oligomers (A) are preferably selected from the group ofcopolymers obtainable by two-stage or multistage controlled free-radicalcopolymerization in an aqueous or an organic medium, particularly in anaqueous medium, where

-   (1) in a first stage    -   (a) at least one olefinically unsatured monomer, in particular        at least one monomer containing at least one, especially one,        anionic and/or potentially anionic and/or nonionic hydrophilic        functional group in the molecule and    -   (b) at least one non-(a) olefinically unsaturated monomer of the        general formula (I)        R¹R²C═CR³R⁴ (I)    -    in which the radicals R¹, R², R³, and R⁴ each independently of        one another are hydrogen atoms or substituted or unsubstituted        alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl,        alkylaryl, cycloalkylaryl, arylalkyl or arylcycloalkyl radicals,        with the proviso that at least two of the variables R¹, R², R³,        and R⁴ are substituted or unsubstituted aryl, arylalkyl or        arylcycloalkyl radicals, especially substituted or unsubstituted        aryl radicals;-    are copolymerized and then-   (2) in a second stage at least one further monomer (a), preferably    at least one monomer (a) containing no anionic and/or potentially    anionic and/or nonionic hydrophilic functional groups, is    (co)polymerized in the presence of the copolymer formed in the first    stage, following the addition of small amounts, or without the    addition, of free-radical initiators.

Examples of highly suitable monomers (a) containing the above-describedanionic and/or potentially anionic functional groups are acrylic acid,beta-carboxyethyl acrylate, methacrylic acid, ethacrylic acid, crotonicacid, maleic acid, fumaric acid or itaconic acid; olefinicallyunsaturated sulfonic or phosphonic acids or their partial esters; ormono(meth)acryloyloxyethyl maleate, succinate or phthalate, especiallyacrylic acid and methacrylic acid.

Besides the above-described monomers (a) containing anionic and/orpotentially anionic functional groups, or instead of them, it is alsopossible to use hydrophilic monomers (a) which contain nonionichydrophilic groups. Preferred hydrophilic groups are polyethylene oxidegroups, preferably oligomeric polyethylene oxide groups up a molecularweight of 400 daltons. The amount of such groups in the copolymers (A)may vary very widely and is preferably in accordance with the amount ofthe anionic and/or potentially anionic groups that is present.

Examples of highly suitable hydrophilic monomers (a) containingfunctional groups of this kind are omega-hydroxy- oromega-methoxy-polyethylene oxide-1-yl, omega-methoxy-polypropyleneoxide-1-yl or omega-methoxy-poly(ethylene oxide-co-polypropyleneoxide)-1-yl acrylate or methacrylate.

Furthermore, it is possible as well to use monomers (a) which contain nopotentially anionic and/or anionic groups and no nonionic hydrophilicgroups. These monomers (a) may be hydrophobic.

Regarding the terms “hydrophilic” and “hydrophobic”, refer to RömppLexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York,1998, page 294, “hydrophilicity” and pages 294 and 295,“hydrophobicity”.

Examples of suitable olefinically unsaturated monomers (a) of this kindare

-   (1) esters of olefinically unsaturated acids, said esters being    substantially free of acid groups, such as (meth)acrylic, crotonic,    ethacrylic, vinylphosphonic or vinylsulfonic alkyl or cycloalkyl    esters having up to 20 carbon atoms in the alkyl radical, especially    methyl, ethyl, propyl, n-butyl, sec-butyl, tert-butyl, hexyl,    ethylhexyl, stearyl, and lauryl acrylate, meth-acrylate, crotonate,    ethacrylate or vinylphosphonate or vinylsulfonate; cycloaliphatic    (meth)acrylic, crotonic, ethacrylic, vinylphosphonic or    vinylsulfonic esters, especially cyclohexyl, isobornyl,    dicyclopentadienyl, octahydro-4,7-methano-1H-indenemethanol or    tert-butylcyclohexyl (meth)acrylate, crotonate, ethacrylate,    vinylphosphonate or vinylsulfonate. In minor amounts, these monomers    may include more highly functional alkyl or cycloalkyl esters of    (meth)acrylic acid, crotonic acid or ethacrylic acid, such as    ethylene glycol, propylene glycol, diethylene glycol, dipropylene    glycol, butylene glycol, pentane-1,5-diol, hexane-1,6-diol,    octahydro-4,7-methano-1H-indenedimethanol or cyclohexane-1,2-, -1,3-    or -1,4-diol di(meth)acrylate; trimethylolpropane tri(meth)acrylate;    or pentaerythritol tetra(meth)acrylate, and the analogous    ethacrylates or crotonates. In the context of the present invention,    minor amounts of more highly functional monomers (1) are amounts    which do not lead to crosslinking or gelling of the copolymers (A),    unless they are intended to be in the form of crosslinked microgel    particles;-   (2) monomers which carry at least one hydroxyl group or    hydroxymethylamino group per molecule and are substantially free of    acid groups, such as    -   hydroxyalkyl esters of alpha,beta-olefinically unsaturated        carboxylic acids, such as hydroxyalkyl esters of acrylic acid,        methacrylic acid and ethacrylic acid in which the hydroxyalkyl        group contains up to 20 carbon atoms, such as 2-hydroxyethyl,        2-hydroxypropyl, 3-hydroxypropyl, 3-hydroxybutyl, 4-hydroxybutyl        acrylate, methacrylate or ethacrylate;        1,4-bis(hydroxymethyl)cyclohexane,        octahydro-4,7-methano-1H-indene-dimethanol or methylpropanediol        monoacrylate, monomethacrylate, monoethacrylate or        monocrotonate; or reaction products of cyclic esters, such as        epsilon-caprolactone, and these hydroxyalkyl esters;    -   olefinically unsaturated alcohols such as allyl alcohol;    -   allyl ethers of polyols, such as trimethylolpropane monoallyl        ether or pentaerythritol monoallyl, diallyl or triallyl ether.        The monomers (2) of higher functionality are generally used only        in minor amounts. In the context of the present invention, minor        amounts of more highly functional monomers are those amounts        which do not lead to crosslinking or gelling of the block        copolymers (A), unless they are intended to be in the form of        crosslinked microgel particles;    -   reaction products of alpha,beta-olefinically unsaturated        carboxylic acids with glycidyl esters of an alpha-branched        monocarboxylic acid having from 5 to 18 carbon atoms in the        molecule. The reaction of acrylic or methacrylic acid with the        glycidyl ester of a carboxylic acid having a tertiary alpha        carbon atom may take place before, during or after the        polymerization reaction. As component (a1) it is preferred to        use the reaction product of acrylic acid and/or methacrylic acid        with the glycidyl ester of Versatic® acid. This glycidyl ester        is available commercially under the name Cardura® E10. For        further details, refer to Römpp Lexikon Lacke und Druckfarben,        Georg Thieme Verlag, Stuttgart, New York, 1998, pages 605 and        606;    -   formaldehyde adducts of aminoalkyl esters of        alpha,beta-olefinically unsaturated carboxylic acids and of        alpha,beta-unsaturated carboxamides, such as N-methylol- and        N,N-dimethylolaminoethyl acrylate, -aminoethyl methacrylate,        -acrylamide, and -methacrylamide; and also    -   olefinically unsaturated monomers containing acryloyloxysilane        groups and hydroxyl groups, preparable by reacting        hydroxy-functional silanes with epichlorohydrin and then        reacting the intermediate with an alpha,beta-olefinically        unsaturated carboxylic acid, especially acrylic acid and        methacrylic acid, or hydroxyalkyl esters thereof;-   (3) vinyl esters of alpha-branched monocarboxylic acids having from    5 to 18 carbon atoms in the molecule, such as the vinyl esters of    Versatic® acid, which are sold under the brand name VeoVa®;-   (4) cyclic and/or acyclic olefins, such as ethylene, propylene,    but-1-ene, pent-1-ene, hex-1-ene, cyclohexene, cyclopentene,    norbornene, butadiene, isoprene, cyclopentadiene and/or    dicyclopentadiene;-   (5) amides of alpha,beta-olefinically unsaturated carboxylic acids,    such as (meth)acrylamide, N-methyl-, N,N-dimethyl-, N-ethyl-,    N,N-diethyl-, N-propyl-, N,N-dipropyl-, N-butyl-, N,N-dibutyl-    and/or N,N-cyclohexyl-methyl-(meth)acrylamide;-   (6) monomers containing epoxide groups, such as the glycidyl ester    of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid,    maleic acid, fumaric acid and/or itaconic acid;-   (7) vinylaromatic hydrocarbons, such as styrene, vinyltoluene or    alpha-alkylstyrenes, especially alpha-methylstyrene;-   (8) nitriles, such as acrylonitrile or methacrylonitrile;-   (9) vinyl compounds, selected from the group consisting of vinyl    halides such as vinyl chloride, vinyl fluoride, vinylidene    dichloride, and vinylidene difluoride; vinylamides, such as    N-vinylpyrrolidone; vinyl ethers such as ethyl vinyl ether, n-propyl    vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl    vinyl ether, and vinyl cyclohexyl ether; and also vinyl esters such    as vinyl acetate, vinyl propionate, and vinyl butyrate;-   (10) allyl compounds, selected from the group consisting of allyl    ethers and allyl esters, such as propyl allyl ether, butyl allyl    ether, ethylene glycol diallyl ether, and trimethylolpropane    triallyl ether, and allyl acetate and allyl propionate; regarding    the monomers of higher functionality, the comments made above apply    analogously;-   (11) monomers containing siloxane groups, such as    methacryloyloxypropyltrimethoxysilane (MEMO); and-   (12) polysiloxane macromonomers having a number average molecular    weight Mn of from 1000 to 40,000 and containing on average from 0.5    to 2.5 ethylenically unsaturated double bonds per molecule, such as    polysiloxane macromonomers having a number average molecular weight    Mn of from 1000 to 40,000 ethylenically unsaturated double bonds per    molecule; especially polysiloxane macromonomers having a number    average molecular weight Mn of from 2000 to 20,000, with particular    preference from 2500 to 10,000, and in particular from 3000 to 7000    and containing on average from 0.5 to 2.5, preferably from 0.5 to    1.5, ethylenically unsaturated double bonds per molecule, as are    described in DE 38 07 571 A 1 on pages 5 to 7, in DE 37 06 095 A 1    in columns 3 to 7, in EP 0 358 153 B 1 on pages 3 to 6, in U.S. Pat.    No. 4,754,014 A 1 in columns 5 to 9, in DE 44 21 823 A 1, or in the    international patent application WO 92/22615 on page 12 line 18 to    page 18 line 10.

As monomers (b) compounds of the general formula I are used.

In the general formula I the radicals R¹, R², R³, and R⁴ eachindependently of one another are hydrogen atoms or substituted orunsubstituted alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl,alkylaryl, cycloalkylaryl, arylalkyl or arylcycloalkyl radicals, withthe proviso that at least two of the variables R¹, R², R³ and R⁴ aresubstituted or unsubstituted aryl, arylalkyl or arylcycloalkyl radicals,especially substituted or unsubstituted aryl radicals.

Examples of suitable alkyl radicals are methyl, ethyl, propyl,isopropyl, n-butyl, isobutyl, tert-butyl, amyl, hexyl, and 2-ethylhexyl.

Examples of suitable cycloalkyl radicals are cyclobutyl, cyclopentyl,and cyclohexyl.

Examples of suitable alkylcycloalkyl radicals are methylenecyclohexane,ethylenecyclohexane, and propane-1,3-diylcyclohexane.

Examples of suitable cycloalkylalkyl radicals are 2-, 3-, and 4-methyl-,-ethyl-, -propyl-, and -butylcyclohex-1-yl.

Examples of suitable aryl radicals are phenyl, naphthyl, and biphenylyl.

Examples of suitable alkylaryl radicals are benzyl and ethylene- andpropane-1,3-diylbenzyl.

Examples of suitable cycloalkylaryl radicals are 2-, 3- and4-phenylcyclohex-1-yl.

Examples of suitable arylalkyl radicals are 2-, 3-, and 4-methyl-,-ethyl-, -propyl-, and -butylphen-1-yl.

Examples of suitable arylcycloalkyl radicals are 2-, 3- and4-cyclohexylphen-1-yl.

The above-described radicals R¹, R², R³, and R⁴ may be substituted. Forthis purpose, electron withdrawing or electron donating atoms or organicradicals may be used.

Examples of suitable substituents are halogen atoms, especially chlorineand fluorine, nitrile groups, nitro groups, partially or fullyhalogenated, especially chlorinated and/or fluorinated, alkyl,cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl,cycloalkylaryl, arylalkyl, and arylcycloalkyl radicals, including thoseexemplified above, especially tert-butyl; aryloxy, alkyloxy, andcycloalkyloxy radicals, especially phenoxy, naphthoxy, methoxy, ethoxy,propoxy, butyloxy or cyclohexyloxy; arylthio, alkylthio, andcycloalkylthio radicals, especially phenylthio, naphthylthio,methylthio, ethylthio, propylthio, butylthio, and cyclohexylthio; and/orhydroxyl groups.

Examples of monomers (b) used with particular preference in accordancewith the invention are 1,1-diphenylethylene, 1,1-dinaphthaleneethylene,cis- and trans-stilbene, and vinylidenebis(4-nitrobenzene).

In accordance with the invention, the monomers (b) may be usedindividually or as a mixture of at least two monomers (b).

With regard to the reaction regime and the properties of the resultingcopolymers (A), 1,1-diphenylethylene is of very particular advantage andis therefore used with very particular preference in accordance with theinvention.

Each of the abovementioned monomers containing anionic and/orpotentially anionic functional groups (a) may be polymerized on its ownwith the monomer (b). In accordance with the invention, however, it isof advantage to use at least one further monomer (a) that is free ofthese functional groups, since by this means the profile of propertiesof the resulting copolymers in stage (1) may, in a particularlyadvantageous manner, be varied very broadly and custom-tailored to therespective end use of the dispersions of the invention. The monomers (a)are preferably selected so that the profile of properties of thecopolymers (A) is substantially determined by the above-described(meth)acrylate monomers (a), with the monomers (a) from other classesbroadly and purposively varying this profile of properties in anadvantageous manner. By this means, in particular, functional groups bymeans of which the copolymers (A) become hydrophilic, so that they canbe dissolved or dispersed in aqueous media, can be incorporated into theblock copolymers (A). It is also possible to incorporate reactivefunctional groups which are able to enter into thermal crosslinkingreactions with the complementary reactive functional groups (S2),described below, in the compounds II described below. Moreover, it ispossible to incorporate functional groups which give the copolymers (A)self-crosslinking properties, such as N-methylol or N-alkoxymethyl orN-methylol ether groups. Incorporated into the copolymers (A) not leastmay be at least one of the reactive functional groups (S1) describedbelow, containing at least one bond which can be activated with actinicradiation, which are able to react with any bonds which can be activatedwith actinic radiation that are present in the compounds II describedbelow. Of course, both kinds of reactive functional groups (S1) and (S2)may be incorporated into the copolymers (A). The copolymers (A) inquestion are in that case curable both thermally and with actinicradiation, something which is referred to by those in the art as dualcure.

Here and below, actinic radiation means electromagnetic radiation, suchas near infrared (NIR), visible light, UV radiation or X-rays,especially UV radiation, and corpuscular radiation, such as electronbeams.

The copolymer (A) may therefore contain at least one, preferably atleast two, reactive functional groups (S2) which are able to enter intothermal crosslinking reactions with complementary reactive functionalgroups (S2) of the compounds II described below. These reactivefunctional groups may be incorporated into the copolymers (A) by way ofthe monomers (a), or may be introduced by means of polymer-analogousreactions following the synthesis of said copolymers. It should beensured here that the reactive functional groups (S2) do not undergo anyunwanted reactions with one another or with the aqueous medium, such as,for example, unwanted salt formation, the formation of insolubleprecipitates, or premature crosslinking, all of which adversely affectthe stability of the dispersion of the invention.

Examples of suitable complementary reactive functional groups (S2) foruse in accordance with the invention that enter into crosslinkingreactions are compiled in the overview below. In the overview, thevariable R⁵ stands for substituted or unsubstituted alkyl, cycloalkyl,alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl, cycloalkylaryl,arylalkyl or arylcycloalkyl radicals. Examples of suitable such radicalsare those recited above in connection with the radicals R¹, R², R³, andR⁴.

Overview: Examples of Complementary Functional Groups (S2) Copolymer (A)and or compound II Compound II and copolymer (A) —SH —C(O)—OH —OH—C(O)—O—C(O)— —NH—C(O)—OR⁵ —CH₂—OH —CH₂—O—CH₃ —NH—C(O)—CH(—C(O)OR⁵)₂—NH—C(O)—CH(—C(O)OR⁵)(— C(O)—R⁵) >Si(OR⁵)₂ —C(O)—OH

—O—C(O)—CR⁵═CH₂ —OH —O—CR═CH₂ —C(O)—CH₂—C(O)—R⁵ —CH═CH₂

The copolymers (A) are preferably prepared by reacting, in a first stage(1), at least one monomer (b) with at least one monomer (a) containingat least one potentially anionic or anionic functional group, to form acopolymer or a macroinitiator. This copolymer or this macroinitiator isthen, in at least one further stage (2), following its isolation ordirectly in the reaction mixture, preferably directly in the reactionmixture, reacted with at least one further, preferably hydrophobic,monomer (a) containing no potentially anionic, anionic or nonionichydrophilic groups, under free-radical conditions.

The reaction in stage (2) is preferably carried out following theaddition of a small amount, or without the addition, of a free-radicalpolymerization initiator. Small amounts are amounts below the amounts ofinitiators used in stage (1) in each case. This means that reaction instage (2) can be carried out in the complete absence of an initiator orcan be carried out and initiated by the remnants of the initiator usedin stage (1) or by an initiator added in the comparable amount.

Alternatively, stages (1) and (2) may also be conducted in succession inone reactor. For this purpose, first of all the monomer (b) is reactedwith at least one monomer (a), completely or partly, depending on thedesired application and desired properties, after which at least onefurther monomer (a) is added and the mixture is subjected tofree-radical polymerization. In another embodiment, at least twomonomers (a) are used from the start, with the monomer (b) reactingfirst with one of the at least two monomers (a) and then the resultingcopolymer, above a certain molecular weight, also reacting with thefurther monomer(s) (a).

Preferably, the weight ratio of the copolymer or macroinitiator formedin the first stage (1) to the further monomer(s) (a) of the furtherstage(s) (2) is from 1:25 to 5:1, more preferably from 1:22 to 4:1, withparticular preference from 1:18 to 3:1, with very particular preferencefrom 1:16 to 2:1, and in particular from 1:15 to 1:1.

Depending on reaction regime it is possible to prepare copolymers (A)having block, multiblock, gradient (co)polymer, star, and branchedstructures, with or without functionalization on the end groups.

Examples of the free-radical polymerization initiators which may be usedin the first stage (1) include the following: dialkyl peroxides, such asdi-tert-butyl peroxide or dicumyl peroxide; hydroperoxides, such ascumene hydroperoxide or tert-butyl hydroperoxide; peresters, such astert-butyl perbenzoate, tert-butyl perpivalate, tert-butylper-3,5,5-trimethylhexanoate or tert-butyl per-2-ethylhexanoate;potassium, sodium or ammonium peroxodisulfate; azo dinitriles such asazobisisobutyronitrile; C—C-cleaving initiators such as benzpinacolsilyl ethers; or a combination of a nonoxidizing initiator with hydrogenperoxide. Further examples of suitable initiators are described in theGerman patent application DE 196 28 142 A1, page 3 line 49 to page 4line 6.

It is preferred in stage (1) to add comparatively large amounts offree-radical initiator, with the fraction of the initiator in thereaction mixture, based in each case on the overall amount of themonomers (a) and (b) and the initiator, being with particular preferencefrom 0.5 to 50% by weight, with very particular preference from 1 to 20%by weight, and in particular from 2 to 15% by weight.

The weight ratio of initiator to monomers (b) is preferably from 4:1 to1:4, with particular preference from 3:1 to 1:3, and in particular from2:1 to 1:2. Further advantages result if the initiator is used in excesswithin the stated limits.

The two-stage or multistage free-radical copolymerization orcopolymerization is preferably conducted in an aqueous medium.

The aqueous medium comprises substantially water. Said aqueous mediummay contain minor amounts of dissolved solid, liquid or gaseous, lowand/or high molecular mass substances, especially bases, provided thesedo not adversely affect, let alone inhibit, the copolymerization and/ordo not lead to the emission of volatile organic compounds. In thecontext of the present invention, the term “minor amount” means anamount which does not destroy the aqueous nature of the aqueous medium.This aqueous medium may, however, also be water alone.

Examples of suitable bases are low molecular mass bases such as sodiumhydroxide solution, potassium hydroxide solution, ammonia,diethanolamine, triethanolamine, mono-, di-, and triethylamine, and/ordimethylethanolamine, especially ammonia and/or di- and/ortriethanolamine.

In accordance with the invention it is of advantage if the aqueousmedium used in stage (1) forms at least the majority, especially theentirety, of the aqueous medium in which the copolymer (A) is present indispersion following its preparation.

In accordance with the invention it is further of advantage if theaqueous medium contains the copolymer formed in stage (1) in an amount,based on the total amount of aqueous medium and copolymer, of from 0.1to 10%, preferably from 1 to 8%, and in particular from 2 to 7% byweight.

Suitable reactors for the (co)polymerization processes are the customaryand known stirred tanks, stirred tank cascades, tube reactors, loopreactors or Taylor reactors, as described for example in the patents DE198 28 742 A 1 and EP 0 498 583 A 1 or in the article by K. Kataoka inChemical Engineering Science, Volume 50, No. 9, 1995, pages 1409 to1416. The free-radical copolymerization is preferably conducted instirred tanks or Taylor reactors, the Taylor reactors being designed sothat the conditions of Taylor flow are met over the entire length of thereactor, even if there is a sharp change—especially an increase—in thekinematic viscosity of the reaction medium owing to copolymerization(cf. the German patent application DE 198 28 742 A 1).

The copolymerization is advantageously conducted at temperatures aboveroom temperature and below the lowest decomposition temperature of therespective monomers used, preference being given to the choice oftemperature range from 10 to 150° C., with very particular preferencefrom 50 to 120° C., and in particular from 55 to 110° C.

When using particularly volatile monomers (a) and/or (b), thecopolymerization may also be conducted under pressure, preferably underfrom 1.5 to 3000 bar, more preferably from 5 to 1500 bar, and inparticular from 10 to 1000 bar.

As far as the molecular weight distribution is concerned, the copolymer(A) is not subject to any restrictions whatsoever. Advantageously,however, the copolymerization is conducted so as to give a ratio Mw/Mn,measured by gel permeation chromatography using polystyrene as standard,of ≦4, preferably ≦2, and in particular ≦1.5, and, in certain cases,even ≦1.3. The molecular weights of the copolymers (A) can be controlledwithin wide limits through the choice of the ratio of monomer (a) tomonomer (b) to free-radical initiator. In this relationship, it is theamount of monomer (b) in particular that determines the molecularweight, specifically such that, the greater the fraction of monomer (b),the lower the molecular weight obtained.

The amount of the copolymer (A) in the dispersion of the invention mayvary widely and is guided by the requirements of the case in hand.Preferably, the copolymer (A) is present in the dispersion of theinvention in an amount, based on the sum of the essential constituents(A), (B), and (C), of from 1 to 30% by weight.

The further essential constituent of the dispersion of the inventioncomprises surface-modified, cationically stabilized, inorganicnanoparticles (B) of at least one kind, particularly of one kind.

The nanoparticles to be modified are preferably selected from the groupconsisting of main group and transition group metals and theircompounds. The main group and transition group metals are preferablyselected from metals of main groups three to five, transition groupsthree to six and also one and two of the periodic system of theelements, and the lanthanides. Particular preference is given to usingboron, aluminum, gallium, silicon, germanium, tin, arsenic, antimony,silver, zinc, titanium, zirconium, hafnium, vanadium, niobium, tantalum,molybdenum, tungsten, and cerium, especially aluminum, silicon, silver,cerium, titanium, and zirconium.

The compounds of the metals are preferably the oxides, oxide hydrates,sulfates or phosphates.

Preference is given to using silver, silicon dioxide, aluminum oxide,aluminum oxide hydrate, titanium dioxide, zirconium oxide, cerium oxide,and mixtures thereof, with particular preference silver, cerium oxide,silicon dioxide, aluminum oxide hydrate, and mixtures thereof, with veryparticular preference aluminum oxide hydrate, and especially boehmite.

The nanoparticles to be modified preferably have a primary particle size<50 nm, more preferably from 5 to 50 μm, in particular from 10 to 30 nm.

The nanoparticles (B) for use in accordance with the invention, or theirsurface, are modified with at least one compound of the general formulaII:[(S-)_(o)-L-]_(m)M(R)_(n)(H)_(p)  (II).

In the general formula II the indices and variables have the followingmeanings:

-   S is a reactive functional group;-   L is an at least divalent organic linking group;-   H is a hydrolyzable monovalent group or a hydrolyzable atom;-   M is a divalent to hexavalent main group or transition group metal;-   R is a monovalent organic radical;-   o is an integer from 1 to 5, especially 1;-   m+n+p is an integer from 2 to 6, especially 3 or 4;-   p is an integer from 1 to 6, especially from 1 to 4;-   m and n are zero or an integer from 1 to 5, preferably from 1 to 3,    in particular 1, especially m=1 and n=0.

Said modification may be effected by physical adsorption of thecompounds II onto the surface of the unmodified nanoparticles and/or bychemical reaction of the compounds II with suitable reactive functionalgroups on the surface of the unmodified nanoparticles. Preferably, themodification is effected by way of chemical reactions.

Examples of suitable metals M are those described above.

The reactive functional group S is preferably selected from the groupconsisting of (S1) reactive functional groups which contain at least onebond which can be activated with actinic radiation and (S2) reactivefunctional groups which undergo thermally initiated reactions withgroups of their own kind (“with themselves”) and/or with complementaryreactive functional groups. Examples of suitable reactive functionalgroups (S2) are those described above, especially epoxide groups.

In the context of the present invention a bond which can be activatedwith actinic radiation is a bond which on exposure to actinic radiationbecomes reactive and, with other activated bonds of its kind, entersinto polymerization reactions and/or crosslinking reactions whichproceed in accordance with free-radical and/or ionic mechanisms.Examples of suitable bonds are carbon-hydrogen single bonds orcarbon-carbon, carbon-oxygen, carbon-nitrogen, carbon-phosphorus orcarbon-silicon single bonds or double bonds. Of these, the carbon-carbondouble bonds are particularly advantageous and are therefore used withvery particular preference in accordance with the invention. For thesake of brevity they are referred to below as “double bonds”.

Accordingly, the inventively preferred reactive group (S1) contains onedouble bond or two, three or four double bonds. Where more than onedouble bond is used, the double bonds may be conjugate. In accordancewith the invention, however, it is an advantage if the double bonds areisolated, in particular each terminally, within the group (S1) inquestion. It is of particular advantage in accordance with the inventionto use two double bonds, especially one double bond.

The bonds which can be activated with actinic radiation may be connectedto the linking group L by way of carbon-carbon bonds or ether,thioether, carboxylate, thiocarboxylate, carbonate, thiocarbonate,phosphate, thiophosphate, phosphonate, thiophosphonate, phosphite,thiophosphite, sulfonate, amide, amine, thioamide, phosphoramide,thiophosphoramide, phosphonamide, thiophosphonamide, sulfonamide, imide,urethane, hydrazide, urea, thiourea, carbonyl, thiocarbonyl, sulfone orsulfoxide groups, but in particular by way of carbon-carbon bonds,carboxylate groups, and ether groups.

Particularly preferred reactive functional groups (S1) are therefore(meth)acrylate, ethacrylate, crotonate, cinnamate, vinyl ether, vinylester, dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, allyl orbutenyl groups; dicyclopentadienyl ether, norbornenyl ether, isoprenylether, isopropenyl ether, allyl ether or butenyl ether groups; ordicyclopentadienyl ester, norbornenyl ester, isoprenyl ester,isopropenyl ester, allyl ester or butenyl ester groups, but especiallymethacrylate groups (S1).

The variable H stands for a hydrolyzable monovalent group or for ahydrolyzable atom.

Examples of suitable hydrolyzable atoms are hydrogen atoms and halogenatoms, especially chlorine and bromine atoms.

Preferably, the hydrolyzable monovalent groups are used. Examples ofsuitable groups of this kind are groups of the general formula III:—X—R (III).

In the general formula III the variable X stands for an oxygen atom,sulfur atom and/or group >NR⁶, in which R⁶ denotes an alkyl group havingfrom 1 to 4 carbon atoms, especially methyl, ethyl, propyl, and n-butyl.Preferably, X stands for an oxygen atom.

R stands for a monovalent organic radical. The monovalent radical R maybe substituted or unsubstituted; preferably, it is unsubstituted. It maybe aromatic, aliphatic or cycloaliphatic. A monovalent radical R isregarded as aromatic when X is connected directly to the aromaticradical. This rule is to be applied mutatis mutandis to the aliphaticand cycloaliphatic radicals. Preference is given to using linear orbranched, especially linear, aliphatic radicals. Lower aliphaticradicals are preferred, especially the aliphatic radicals R¹ describedabove. Of these, the methyl groups or the ethyl groups are used withvery particular preference.

The variable L stands for an at least divalent, especially divalent,organic linking group.

Examples of suitable divalent organic linking groups L are aliphatic,aromatic, cycloaliphatic, and aromatic-cycloaliphatic, and alsoheteroatoms-containing aliphatic, aromatic, cycloaliphatic, andaromatic-cycloaliphatic, hydrocarbon radicals, such as

-   (1) substituted or unsubstituted, preferably unsubstituted, linear    or branched, preferably linear, alkanediyl radicals having from 3 to    30, preferably from 3 to 20, and in particular 3 carbon atoms, which    may also contain cyclic groups within the carbon chain, especially    trimethylene, tetramethylene, pentamethylene, hexamethylene,    heptamethylene, octamethylene, nonane-1,9-diyl, decane-1,10-diyl,    undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl,    tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl,    heptadecane-1,17-diyl, octadecane-1,18-diyl, nonadecane-1,19-diyl or    eicosane-1,20-diyl preferably tetramethylene, pentamethylene,    hexamethylene, heptamethylene, octamethylene, nonane-1,9-diyl,    decane-1,10-diyl, 2-heptyl-1-pentylcyclohexane-3,4-bis(non-9-yl),    cyclohexane-1,2-, -1,4- or -1,3-bis(methyl), cyclohexane-1,2-, -1,4-    or -1,3-bis(eth-2-yl), cyclohexane-1,3-bis(prop-3-yl) or    cyclohexane-1,2-, -1,4- or -1,3-bis(but-4-yl);-   (2) substituted or unsubstituted, preferably unsubstituted, linear    or branched, preferably linear, oxaalkanediyl radicals having from 3    to 30, preferably from 3 to 20, and in particular from 3 to 6 carbon    atoms, which may also contain cyclic groups within the carbon chain,    especially oxapropane-1,4-diyl, oxabutane-1,5-diyl,    oxapentane-1,5-diyl, oxahexane-1,7-diyl or 2-oxapentane-1,5-diyl;-   (3) divalent polyester radicals containing repeating polyester units    of the formula —(—CO—(CHR⁷)_(r)—CH₂—O—)—. In this formula the index    r is preferably from 4 to 6 and the substituent R⁷=hydrogen, or an    alkyl, cycloalkyl or alkoxy radical. No substituent contains more    than 12 carbon atoms;-   (4) linear polyether radicals, preferably having a number-average    molecular weight of from 400 to 5000, in particular from 400 to    3000, which derive from poly(oxyethylene) glycols,    poly(oxypropylene)glycols, and poly(oxybutylene)glycols;-   (5) linear siloxane radicals, as are present, for example, in    silicone rubbers, hydrogenated polybutadiene radicals or    polyisoprene radicals, random or alternating butadiene-isoprene    copolymer radicals or butadiene-isoprene graft copolymer radicals,    which may also contain copolymerized styrene, and also    ethylene-propylene-diene radicals;-   (6) phen-1,4-, -1,3- or -1,2-ylene, naphth-1,4-, -1,3-, -1,2-, -1,5-    or -2,5-ylene, propane-2,2-di(phen-4′-yl), methane-di(phen-4′-yl),    biphenyl-4,4′-diyl or 2,4- or 2,6-tolylene; or-   (7) cycloalkanediyl radicals having from 4 to 20 carbon atoms, such    as cyclobutane-1,3-diyl, cyclopentane-1,3-diyl, cyclohexane-1,3- or    -1,4-diyl, cycloheptane-1,4-diyl, norbornane-1,4-diyl,    adamantane-1,5-diyl, decalindiyl,    3,3,5-trimethylcyclohexane-1,5-diyl, 1-methylcyclohexane-2,6-diyl,    dicyclohexylmethane-4,4′-diyl, 1,1′-dicyclohexane-4,4′-diyl or    1,4-dicyclohexylhexane-4,4″-diyl, especially    3,3,5-trimethylcyclohexane-1,5-diyl or    dicyclohexylmethane-4,4′-diyl.

With particular preference, the linking groups L(1) and L(2) are used,with very particular preference trimethylene, tetramethylene,pentamethylene, hexamethylene, heptamethylene, octamethylene,oxapropane-1,4-diyl or 2-oxapentane-1,5-diyl, and especiallytrimethylene, oxapropane-1,4-diyl or 2-oxapentane-1,5-diyl.

In the general formula II the variable o stands for an integer from 1 to5, preferably from 1 to 4, more preferably 1 to 3, and with particularpreference 1 and 2. In particular, o is equal to 1.

The compounds II may also be used in complexed form, as is described,for example, in the international patent application WO 99/52964, page 8lines 12 to 20.

The compounds II are customary and known and to a large extent areavailable commercially. Highly suitable compounds II are known, forexample, from the

-   -   international patent application WO 99/52964, page 6 line 1 to        page 8 line 20,    -   German patent application DE 197 26 829 A1, column 2 line 27 to        column 3 line 38,    -   German patent application DE 199 10 876 A1, page 2 line 35 to        page 3 line 12,    -   German patent application DE 38 28 098 A1, page 2 line 27 to        page 4 line 43, or    -   European patent application EP 0 450 625 A1, page 2 line 57 to        page 5 line 32.

Viewed in terms of its method, the modification of the surface of thenanoparticles has no special features but instead takes place inaccordance with the customary and known methods known, for example, frominternational patent application WO 99/52964, page 10 line 22 to page 11line 17 and examples 1 to 20, page 14 line 10 to page 20 line 24, orfrom German patent application DE 197 26 829 A1, examples 1 to 6, column5 line 63 to column 8 line 38. It is preferred to employ the proportionsstated therein of compounds II to unmodified nanoparticles.

The amount of the surface-modified inorganic nanoparticles (B) in thedispersion of the invention may vary widely and is guided by therequirements of the case in hand. In the dispersion of the invention thenanoparticles (B) are present preferably in an amount, based on the sumof the essential constituents (A), (B), and (C), of from 60 to 98% byweight.

The further essential constituent of the dispersion of the invention isat least one amphiphile (C).

Amphiphiles, as is known, are molecules having both hydrophilic andlipophilic properties (cf. Römpp Chemie Lexikon, Georg Thieme Verlag,Stuttgart, New York, 9th Edition, 1989, Volume 1, page 176,“amphiphile”).

The amphiphiles are preferably selected from the group consisting ofmonoalcohols, especially monoalcohols having from 3 to 6 carbon atoms inthe molecule, and aliphatic polyols, especially diols having from 3 to12 carbon atoms in the molecule.

Examples of highly suitable monoalcohols are propanol, isopropanol,n-butanol, isobutanol, sec-butanol, tert-butanol, amyl alcohol,neopentyl alcohol or n-hexanol.

Examples of suitable diols are propylene glycol, trimethylene glycol,butylene glycol, 1,5-pentanediol, 1,6-hexanediol, and the positionallyisomeric diethyloctanediols, such as are known, for example, from theGerman patent application DE 198 09 643 A1.

Particular preference is given to using propanol, isopropanol, butanolor isobutanol.

The amount of the amphiphiles (C) in the dispersion of the invention mayvary very widely and is guided by the requirements of the case in hand.In the dispersion of the invention the amphiphiles (C) are preferablypresent in an amount, based on the sum of the essential constituents(A), (B), and (C), of from 1 to 10% by weight.

Besides the essential constituents described above, the dispersion ofthe invention may further comprise other constituents customary incoating materials.

It is nevertheless a very particular advantage of the dispersion of theinvention that even without crosslinking agents or additives it providesoutstanding coatings and paint systems or optical moldings andself-supporting films.

The preparation of the dispersion of the invention requires no specialfeatures in terms of method but instead takes place in accordance withthe customary and known methods of preparing aqueous dispersions, bymixing of the above-described constituents in suitable mixing equipmentsuch as stirred tanks, dissolvers, Ultraturrax, inline dissolvers, millswith stirrer mechanism, or extruders.

The dispersion of the invention serves for producing the paint systemsand coatings of the invention on primed or unprimed substrates. It isfurther suitable for all end uses which are described in internationalpatent application WO 99/52964, page 12 line 10 to page 14 line 4,especially for producing optical moldings and self-supporting films.

Suitable substrates include all surfaces to be coated which areundamaged by curing of the coatings present thereon using heat or bothheat and actinic radiation. Suitable substrates are composed, forexample, of metals, plastics, wood, ceramic, stone, textile, fibercomposites, leather, glass, glass fibers, glass wool, rock wool,mineral-bound and resin-bound building materials, such as plasterboardand cement slabs or roof shingles, and also composites of thesematerials. The surfaces of these materials may already be coated.

Accordingly, the dispersion of the invention is especially suitable forcoating motor vehicle bodies and parts thereof, the interior andexterior of motor vehicles, the interior and exterior of buildings,doors, windows, and furniture, and, in industrial coating, for thecoating of plastics parts, especially transparent plastics parts, smallparts, coils, containers, packaging, electrical components, and whitegoods, and also for the coating of hollow glassware.

In the case of electrically conductive substrates it is possible to useprimers, produced conventionally from electrocoat materials. Both anodicand cathodic electrocoat materials may be used for this purpose, butespecially cathodics.

With the coating of the invention it is also possible to coat primed orunprimed plastics such as, for example, ABS, AMMA, ASA, CA, CAB, EP, UF,CF, MF, MPF, PF, PAN, PA, PE, HDPE, LDPE, LLDPE, UHMWPE, PET, PMMA, PP,PS, SB, PUR, PVC, RF, SAN, PBT, PPE, POM, PUR-RIM, SMC, BMC, PP-EPDM,and UP (abbreviations according to DIN 7728T1) and also polymer blendsthereof or the fiber-reinforced composite materials produced using theseplastics.

Unfunctionalized and/or apolar substrate surfaces may be subjected priorto coating in a known manner to a pretreatment, such as with a plasma orby flaming, or may be provided with a hydroprimer.

Particular advantages are displayed by the dispersion of the inventionand the coatings of the invention in automotive OEM finishing andrefinish as clear and transparent, highly scratch-resistant, high-gloss,flexible, acid- and water-resistant, firmly adhering, antistonechipclearcoats as part of multicoat color and/or effect paint systems.

The multicoat paint systems of the invention may be produced in avariety of ways in accordance with the invention.

A first preferred variant of the coating process of the inventioncomprises the steps of

-   (I) preparing a basecoat film by applying an aqueous basecoat    material to the substrate,-   (II) drying the basecoat film,-   (III) preparing a clearcoat film by applying the dispersion of the    invention to the basecoat film, and-   (IV) jointly curing the basecoat film and the clearcoat film of the    invention to give the basecoat and the clearcoat of the invention    (wet-on-wet technique).

This variant offers particular advantages in connection with the coatingof plastics especially and is therefore employed with particularpreference in that utility.

A second preferred variant of the coating process of the inventioncomprises the steps of

-   (I) preparing a surfacer film by applying a surfacer to the    substrate,-   (II) curing the surfacer film to give the surfacer coat,-   (III) preparing a basecoat film by applying an aqueous basecoat    material to the surfacer coat,-   (IV) drying the basecoat film,-   (V) preparing the clearcoat film of the invention by applying the    dispersion of the invention to the basecoat film, and-   (VI) jointly curing the basecoat film and the clearcoat film of the    invention to give the basecoat and the clearcoat of the invention    (wet-on-wet technique).

A third preferred variant of the coating process of the inventioncomprises the steps of

-   (I) preparing a surfacer film by applying a surfacer to the    substrate,-   (II) drying the surfacer film,-   (III) preparing a basecoat film by applying an aqueous basecoat    material to the surfacer coat,-   (IV) drying the basecoat film,-   (V) preparing the clearcoat film of the invention by applying the    dispersion of the invention to the basecoat film, and-   (VI) jointly curing the surfacer film, the basecoat film, and the    clearcoat film of the invention to give the surfacer coat, the    basecoat, and the clearcoat of the invention (extended wet-on-wet    technique).

A fourth preferred variant of the coating process of the inventioncomprises the steps of

-   (I) depositing an electrocoat film on the substrate,-   (II) drying the electrocoat film,-   (III) preparing a first basecoat film by applying a first basecoat    material to the electrocoat film,-   (IIIa) jointly curing the electrocoat film and the first basecoat    film to give the electrocoat and the first basecoat (wet-on-wet    technique),-   (IV) preparing a second basecoat film by applying a second basecoat    material to the first basecoat,-   (V) drying the second basecoat film,-   (VI) preparing the clearcoat film of the invention by applying the    dispersion of the invention to the basecoat film, and-   (VII) jointly curing the second basecoat film and the clearcoat film    of the invention to give the second basecoat and the clearcoat of    the invention (wet-on-wet technique).

The three last-mentioned variants offer particular advantages inconnection in particular with the original finishing of automobilebodies and are therefore employed with very particular preference inthat utility.

It is a very particular advantage of the coatings produced from thedispersion of the invention that they adhere outstandingly even toalready-cured electrocoats, surfacer coats, basecoats or customary andknown clearcoats, and so are outstandingly suitable for automotiverefinish or for the scratchproofing of exposed areas of paintedautomobile bodies.

The dispersion of the invention may be applied by any customary method,such as spraying, knife coating, brushing, flowcoating, dipping,impregnating, trickling or rolling, for example. The substrate to becoated may itself be at rest, with the application equipment or unitbeing moved. Alternatively the substrate to be coated, especially acoil, may be moving, with the application unit being at rest relative tothe substrate or being moved appropriately.

Preference is given to using spray application methods, such ascompressed air spraying, airless spraying, high-speed rotation,electrostatic spray application (ESTA), alone or in conjunction with hotspray applications such as hot air spraying, for example. Applicationcan be made at temperatures of max. 70 to 80° C., so that appropriateapplication viscosities are achieved without the short period of thermalloading being accompanied by any change in or damage to the dispersionof the invention, or its overspray, which may be intended forreprocessing. For instance, hot spraying may be configured in such a waythat the dispersion of the invention is heated only very briefly in thespray nozzle or shortly before the spray nozzle.

The spray booth used for application may be operated, for example, witha circulation system, which may be temperature-controllable, and whichis itself operated with a suitable absorption medium for the overspray,an example being the dispersion of the invention itself.

In general the electrocoat film, surfacer film, basecoat film, andclearcoat film are applied in a wet film thickness such that curingthereof gives coats having the thicknesses which are advantageous andnecessary for their functions. In the case of the electrocoat thisthickness is from 10 to 70 μm, preferably from 10 to 60 μm, withparticular preference from 15 to 50 μm, and in particular from 15 to 45μm; in the case of the surfacer coat it is from 10 to 150 μm, preferablyfrom 10 to 120 μm, with particular preference from 10 to 100 μm, and inparticular from 10 to 90 μm; in the case of the basecoat it is from 5 to50 μm, preferably from 5 to 40 μm, with particular preference from 5 to30 μm, and in particular from 10 to 25 μm; and in the case of theclearcoats of the invention it is from 10 to 100 μm, preferably from 15to 80 μm, with particular preference from 20 to 70 μm, and in particularfrom 25 to 60 μm. It is, however, also possible to employ the multicoatsystem known from European patent application EP 0 817 614 A1,comprising an electrocoat, a first basecoat, a second basecoat, and aclearcoat of the invention, in which the total thickness of the firstand second basecoat is from 15 to 40 μm and the coat thickness of thefirst basecoat amounts to from 20 to 50% of said total thickness.

The surfacer film, basecoat film, and clearcoat film of the inventionmay be cured thermally or both thermally and with actinic radiation(dual cure).

Curing may take place after a certain rest period. This period may havea duration of from 30 s to 2 h, preferably from 1 min to 1 h, and inparticular from 1 min to 45 min. The rest period serves, for example,for leveling and for devolatilization of the paint films or for theevaporation of volatile constituents such as solvents. The rest periodmay be shorted and/or assisted by the application of elevatedtemperatures up to 90° C. and/or by a reduced humidity <10 g water/kgair, especially <5 g/kg air, provided this is not accompanied by anychange in or damage to the coating films, such as premature completecrosslinking, for instance.

The thermal curing has no special features in terms of method butinstead takes place in accordance with the customary and known methods,such as heating in a convection oven or irradiation with IR lamps.Thermal curing here may also take place in stages. Another preferredmethod of curing is that using near infrared (NIR radiation). Particularpreference is given to a process in which the water component is removedrapidly from the wet films. Suitable processes of this kind aredescribed, for example, by Rodger Talbert in Industrial Paint & Powder,04/01, pages 30 to 33, “Curing in Seconds with NIR”, or inGalvanotechnik, volume 90 (11), pages 3098 to 3100, “coating technology,NIR drying in seconds for liquid and powder coatings”.

The thermal curing takes place advantageously at a temperature of from50 to 200° C., with particular preference from 60 to 190° C., and inparticular from 80 to 180° C. for a time of from 1 min up to 2 h, withparticular preference from 2 min up to 1 h, and in particular from 3 minto 45 min.

Additionally, curing with actinic radiation is carried out using UVradiation and/or electron beams. In this case it is preferred to employa dose of from 1000 to 3000, more preferably from 1100 to 2900, withparticular preference from 1200 to 2800, with very particular preferencefrom 1300 to 2700, and in particular from 1400 to 2600 mJ/cm². Whereappropriate, this curing may be supplemented by actinic radiation fromother radiation sources. In the case of electron beams it is preferredto operate under an inert gas atmosphere. This may be ensured, forexample, by supplying carbon dioxide and/or nitrogen directly to thesurface of the coating films. In the case of curing with UV radiation aswell it is possible to operate under inert gas or in an oxygen-depletedatmosphere in order to prevent the formation of ozone.

Curing with actinic radiation is carried out using the customary andknown radiation sources and optical auxiliary measures. Examples ofsuitable radiation sources are flash lamps from the company VISIT, highor low pressure mercury vapor lamps, which may be doped with lead inorder to open up a radiation window up to 405 nm, or electron beamsources. The equipment and conditions for these curing methods aredescribed, for example, in R. Holmes, U.V. and E.B. Curing Formulationsfor Printing Inks, Coatings and Paints, SITA Technology, Academic Press,London, United Kingdom, 1984. Further examples of suitable processes andequipment for curing with actinic radiation are described in Germanpatent application DE 198 18 735 A1, column 10 lines 31 to 61.

In the case of workpieces of complex shape, such as are envisaged forautomobile bodies, those regions not accessible to direct radiation(shadow regions), such as cavities, folds, and other structuralundercuts, may be (partly) cured using pointwise, small-area orall-round emitters, in conjunction with an automatic movement means forthe irradiation of cavities or edges.

Curing here may take place in stages, i.e., by multiple exposure tolight or to actinic radiation. It may also be carried out alternatingly,i.e., by curing alternately with UV radiation and electron beams.

Where thermal curing and curing with actinic radiation are employedtogether, these methods may be used simultaneously or alternatingly.Where the two curing methods are used alternatingly, it is possible, forexample, to begin with the thermal cure and to end with the actinicradiation cure. In other cases it may prove advantageous to begin and toend with the actinic radiation cure.

The multicoat paint systems of the invention have an outstanding profileof properties which is very well balanced in terms of mechanics, optics,corrosion resistance, and adhesion. Accordingly, the multicoat paintsystems of the invention have the high optical quality and intercoatadhesion required by the market and do not give rise to any problemssuch as deficient condensation resistance, mudcracking or levelingdefects or surface textures in the clearcoats of the invention.

In particular, the multicoat paint systems of the invention exhibit anoutstanding metallic effect, an outstanding D.O.I. (distinctiveness ofthe reflected image), a high scratch resistance, and outstanding surfacesmoothness.

Accordingly, the primed or unprimed substrates of the invention thathave been coated with at least one coating of the invention combine aparticularly advantageous profile of performance properties with aparticularly long service life, which makes them particularly valuableeconomically, esthetically, and technically.

EXAMPLES Preparation Examples 1.1 and 1.2

Preparing Dispersions of the Copolymers (A.1) and (A.2) for InventiveUse

Preparation Example 1.1:

1361.7 parts by weight of deionized water were charged to a reactionvessel equipped with a stirrer and three feed vessels and were heated to75° C. Subsequently, at this temperature, three separate feed streamswere metered into this initial charge in parallel and at a uniform rate.Feed stream 1 consisted of 24.4 parts by weight of acrylic acid, 44.0parts by weight of methyl methacrylate and 3.6 parts by weight of1,1-diphenylethylene. Feed stream 2 consisted of 23 parts by weight of a25% strength by weight aqueous ammonia solution. Feed stream 3 consistedof a solution of 5.4 parts by weight of ammonium peroxodisulfate in138.7 parts by weight of deionized water. Feed streams 1 to 3 weremetered in over 30 minutes. After the end of the addition the reactionmixture was stirred at 75° C. for 1 h. It was subsequently heated to 90°C. At this temperature, via a feed stream 4, a monomer mixture of 260parts by weight of n-butyl methacrylate, 208 parts by weight of styrene,334 parts by weight of hydroxyethyl methacrylate and 234.4 parts byweight of ethylhexyl methacrylate was metered in at a uniform rate over4 h. After the end of the addition, there followed a two-hourpostpolymerization period at 90° C. The resultant dispersion forinventive use (A.1) had a solids content of 41.8% by weight.

At pH values from 2 to 7 the copolymer ((A.1) had an electrophoreticmobility <−2 (μm/s)/(V/cm). The electrophoretic mobility was determinedby means of laser Doppler electrophoresis. The measuring equipmentemployed was a Zetasizer® 3000 from Malvem.

Preparation Example 1.2

Preparation example 1 was repeated except that in the second stage themonomer mixture described in that example was replaced by a monomermixture of 191.7 parts by weight of n-butyl methacrylate, 153.4 parts byweight of styrene, 93.3 parts by weight of hydroxypropyl methacrylate,424.9 parts by weight of hydroxyethyl methacrylate and 173.1 parts byweight of ethylhexyl methacrylate. The resulting dispersion forinventive use (A.2) had a solids content of 41.7% by weight.

At pH values from 2 to 7 the copolymer ((A.2) had an electrophoreticmobility <−2 (μm/s)/(V/cm).

Preparation Examples 2.1 to 2.3

The Preparation of Boehmite Sols

Preparation Example 2.1:

2.78 parts by weight of boehmite (Disperal® P 3 from Sasol Germany GmbH)were added to 25 parts by weight of dilute hydrochloric acid (0.1 N) andthe mixture was stirred at room temperature until the boehmite had fullydissolved. The colloidal solution was then treated for 5 minutes in anultrasound bath. The result was the homogeneous boehmite sol (2.1).

Preparation Example 2.2

Preparation example 2.1 was repeated but using 0.1 N acetic acid insteadof hydrochloric acid. The result was the homogeneous boehmite sol (2.2).

Preparation Example 2.3

Preparation example 2.1 was repeated but using 0.1 N formic acid insteadof hydrochloric acid. The result was the homogeneous boehmite sol (2.3).

Preparation Examples 3.1 to 3.4

Preparing dispersions of surface-modified nanoparticles (B.1) to (B.4)

Preparation Example 3.1

20.8 parts by weight of glycidyloxypropyltriethoxysilane were added to27.78 parts by weight of the boehmite sol (2.1) from preparation example2.1. The resultant reaction mixture was stirred at room temperature for10 h. This gave the homogeneous, surface-modified boehmite sol (B.1).

Preparation Example 3.2

Preparation example 3.1 was repeated but using the boehmite sol (2.2)from preparation example 2.2 instead of the boehmite sol (2.1) frompreparation example 2.1. This gave the surface-modified boehmite sol(B.2).

Preparation Example 3.3

Preparation example 3.1 was repeated but using the boehmite sol (2.3)from preparation example 2.3 instead of the boehmite sol (2.1) frompreparation example 2.1. This gave the surface-modified boehmite sol(B.3).

Preparation Example 3.4

27.8 parts by weight of glycidyloxypropyltriethoxysilane were added to27.78 parts by weight of an aqueous solution of cationically stabilizedsilica nanoparticles (Levasil® 200S from Bayer AG). The resultantreaction mixture was stirred at room temperature for 10 h. This gave thesurface-modified silica sol (B.4).

Examples C1 to C4 C=Comparative

Producing the Noninventive Multicoat Paint Systems C1 to C4

The dispersions (B.1) to (B.4) from preparation examples 3.1 to 3.4 wereapplied pneumatically to test panels which had been coated with a curedelectrocoat, surfacer coat, and basecoat (cf. example 1). The resultantclearcoat films C1 to C4 were cured at 140° C. for 22 minutes. Theresultant clearcoats C1 to C4 were highly scratch resistant. However,they could not be produced in coat thicknesses >30 μm since in that casethey showed stress cracks.

Steel panels with clearcoats C1 to C4 free from stress cracks weresubjected to the constant condensation climate test. Partialdelamination occurred after just 240 h.

Example 1

Preparing a Dispersion of the Invention and Producing the MulticoatPaint System of the Invention

4.75 parts by weight of the dispersion (A.1) from preparation example1.1 and 5.0 parts by weight of isopropanol were added to 90.25 parts byweight of the dispersion (B.1) from preparation example 3.1. Theresulting dispersion was stirred at room temperature for 6 h.

The dispersion of the invention was completely stable on storage. Thusduring 30-day storage at room temperature the viscosity rose only from0.2 to 0.4 dPas. Thereafter it was still possible to produce coatingswhich were always clear, transparent, free from surface defects, andhighly scratch-resistant.

Immediately following its preparation, the dispersion was appliedpneumatically to test panels. For that purpose it was adjusted to sprayviscosity (DIN 4 flow cup: 18 s) with a conventional, polyurethane-basedTheological aid, and was sieved (mesh size: 5 μm).

The test panels used were steel bodywork panels pretreated withcommercial zinc phosphate solution. The steel panels were coated insuccession with an electrocoat in a thickness of from 18 to 22 μm (curedat 175° C. for 15 minutes), a conventional surfacer with a thickness offrom 35 to 40 μm (cured at 160° C. for 20 minutes), and a black basecoatwith a thickness of from 12 to 15 μm (cured at 140° C. for 20 minutes).The dispersion of the invention was applied pneumatically using agravity-feed cup-type gun in a plurality of cross-passes. The resultantclearcoat films were cured at 140° C. for 22 minutes and had a thicknessof 35 μm.

The resultant clearcoats were free from stress cracks and other surfacedefects.

The clearcoats were resistant to stone chipping (multiple impact: 2 bar,two times 500 g of steel shot: rating 2 to 3), extremely firmly adhering(cross-cut test and tape tearoff test to DIN EN ISO 2409: GT0/0),flexible (König pendulum hardness: 83), and highly scratch-resistant(delta gloss according to DIN 67530: 4 units after the sand test; 0units after the brush test; after the car wash simulation test: 4 unitswith ethanol cleaning, 23 units without cleaning).

For the sand test, the film surface was loaded with sand (20 g of quartzsilver sand 1.5-2.0 mm). The sand was placed in a beaker (with its basecut off in a planar fashion) which was fixed firmly to the test panel.By means of a motor drive, the panel with the beaker and the sand wasset in shaking movements. The movement of the loose sand caused damageto the film surface (100 double strokes in 20 s). Following sandexposure, the test area was cleaned to remove abraded material, wipedoff carefully under a jet of cold water, and then dried using compressedair. The gloss was measured in accordance with DIN 67530 before andafter damaging (measurement direction perpendicular to the direction ofscratching).

In the case of the brush test, the test panels were stored at roomtemperature for at least 2 weeks before the test was carried out. Theprocedure followed was that described in FIG. 2 of page 28 of thearticle by P. Betz and A. Bartelt, Progress in Organic Coatings, 22(1993), pages 27-37, albeit with modification in respect of the weightused (2000 g instead of the 280 g specified therein). In the test, thefilm surface was damaged using a mesh fabric which had been loaded witha weight. The mesh fabric and the film surface were wetted copiouslywith a laundry detergent solution. The test panel was moved back andforth under the mesh fabric in reciprocating movements by means of amotor drive. The test element was an eraser (4.5×2.0 cm, broad sideperpendicular to the direction of scratching) wrapped with nylon mesh(No. 11, 31 μm mesh size, Tg 50° C.). The applied weight was 2000 g.Prior to each test the mesh fabric was renewed, with the runningdirection of the woven meshes parallel to the direction of scratching.Using a pipette, approximately 1 ml of a freshly stirred 0.25% strengthPersil solution was applied in front of the eraser. The rotary speed ofthe motor was set so as to perform 80 double strokes in a time of 80 s.After the test, the remaining detergent liquid was rinsed off with coldtap water and the test panels were blown dry using compressed air. Thegloss was measured in accordance with DIN 67530 before and afterdamaging (measurement direction perpendicular to the direction ofscratching).

For the car wash simulation test, a laboratory washing unit from AmtecKistler was used (cf. T. Klimmasch, T. Engbert, Technologietage,Cologne, DFO, report volume 32, pages 59 to 66, 1997).

Examples 2 and C5

Producing an Inventive Multicoat Paint System (example 2) and aNoninventive Multicoat Paint System (Example C5)

The inventive dispersion of example 1 was used to produce the inventiveclearcoat of example 2.

The dispersion (B.1) from preparation example 3.1 was used for producingthe noninventive clearcoat of example C5.

The inventive dispersion from example 1 and the dispersion (B.1) frompreparation example 3.1 were applied pneumatically in wedge form to testpanels and cured (cf. the details relating to example 1). The filmthicknesses were from 10 to 80 μm. While the resulting inventiveclearcoat showed no stress cracks even at 80 μm, such cracks occurred inthe noninventive clearcoat (C5) from a film thickness of just 30 μm.

Example 3

Preparing an Inventive Dispersion and Producing an Inventive MulticoatPaint System

4.75 parts by weight of the dispersion (A.1) from preparation example1.1 and 5 parts by weight of n-butanol were added to 90.25 parts byweight of the dispersion (B.1) from preparation example 3.1. Theresulting inventive dispersion was stirred at room temperature for 6 hand then applied to the test panels and cured as described in example 1.The inventive clearcoats (3) obtained had the same outstandingperformance properties as the clearcoats of examples 1 and 2.

Example 4 Preparing an Inventive Dispersion and Producing an InventiveMulticoat Paint System

Example 4 was repeated but using propanol instead of butanol. Theinventive clearcoats obtained had the same outstanding performanceproperties as the clearcoats (1) to (3) of examples 1 to 3.

Example 5 Preparing an Inventive Dispersion and Producing an InventiveMulticoat Paint System

Example 4 was repeated but using isobutanol instead of butanol. Theinventive clearcoats obtained had the same outstanding performanceproperties as the clearcoats of examples 1 to 4.

Example 6

Preparing an Inventive Dispersion and Producing an Inventive MulticoatPaint System

13.25 parts by weight of dispersion (A.2) and preparation example 1.2and 5 parts by weight of isopropanol were added to 81.75 parts by weightof the dispersion (B.2) from preparation example 3.2. The resultinginventive dispersion was stirred at room temperature for 6 h and thenapplied to the test panels and cured as described in example 1.

This gave inventive clearcoats with a thickness of 35 μm which were freefrom stress cracks and other surface defects. They were also extremelyscratch-resistant, which was underlined by the steel wool scratch test(rating 1).

The steel wool scratch test was carried out using a hammer to DIN 1041(weight without shaft: 800 g; shaft length: 35 cm). The test panels werestored at room temperature for 24 h prior to the test.

The flat side of the hammer was wrapped with a ply of steel wool andfastened to the upturned sides using adhesive tape with a creped backing(Tesakrepp). The hammer was placed onto the clearcoats at right angles.The weighted part of the hammer was guided over the surface of theclearcoats in a track without tipping and without additional physicalforce.

For each test, 10 double strokes were performed within a period of about15 s. After every tenth individual test, the steel wool was replaced.

Following exposure, the test panels were cleaned with a soft cloth toremove residues of steel wool. The test areas were evaluated visuallyunder artificial light and rated as follows: Rating Damage 1 none 2slight 3 moderate 4 moderate to middling 5 severe 6 very severe

Evaluation was carried out immediately after the end of the test.

Example 7

Preparing an Inventive Dispersion and Producing an Inventive MulticoatPaint System

Example 6 was repeated but using dispersion (B.3) from preparationexample 3.3 instead of dispersion (B.2) from preparation example 3.2.The same outstanding results as in example 6 were obtained.

Example 8

Preparing an Inventive Dispersion and Producing an Inventive MulticoatPaint System

Example 6 was repeated but using dispersion (B.4) from preparationexample 3.4 instead of dispersion (B.2) from preparation example 3.2.The same outstanding results as in examples 6 and 7 were obtained.

Example 9

Producing an Inventive Color Multicoat Paint System by the Wet-On-WetTechnique

Example 1 was repeated except that prior to the application of theinventive dispersion the aqueous basecoat film was not cured but insteadwas dried at 100° C. for 10 minutes. Then the aqueous basecoat film andthe inventive clearcoat film were cured jointly at 140° C. for 20minutes.

The thickness of the inventive clearcoat was 35 μm. It was free fromstress cracks and other surface defects. The gloss according to DIN67530 was more than 90 units. The clearcoat was extremely scratchresistant (steel wool scratch test: rating 1).

Example 10

Preparing an Inventive Dispersion and Producing an Inventive MulticoatPaint System

Preparation example 3.1 was repeated except that the alcohol formed as aresult of the condensation was removed from the boehmite sol (3.1) ofpreparation example 3.1 by vacuum distillation at a water bathtemperature of not more than 40° C.

4.75 parts by weight of the dispersion (A.1) from preparation example1.1 and 5 parts by weight of isopropanol were added to 90.25 parts byweight of the alcohol-free boehmite sol. The resulting inventivedispersion was stirred at room temperature for 6 h. It had a volatileorganic substances content of only 5% by weight. It was subsequentlyapplied to test panels and cured as described in example 1. Theresultant inventive clearcoat of the multicoat paint system had athickness of 35 μm and was free from stress cracks and other surfacedefects.

Examples 11 to 14

Preparing Inventive Dispersions and Producing Inventive Multicoat PaintSystems

Examples 1 and 3 to 5 were repeated except that the dispersion (A.2)from preparation example 1.2 was used instead of the dispersion (A.1)from preparation example 1.1.

The resulting inventive dispersions of examples 11 to 14 were applied totest panels and cured as described in example 1. In the inventiveclearcoats of examples 11 to 14, with a thickness of 35 μm, the sameoutstanding results as in examples 1 and 3 to 5 were obtained. Inparticular, the inventive clearcoats of examples 11 to 14 were highlyscratch resistant (steel wool scratch test: rating 1).

Example 15

Preparing an Inventive Dispersion and Producing an Inventive Clearcoaton Glass

13.25 parts by weight of the dispersion (A.2) of preparation example 1.2and 5 parts by weight of isopropanol were added to 81.75 parts by weightof the dispersion (B.1) from preparation example 3.1. The resultinginventive dispersion was stirred at room temperature for 6 h. It wasthen applied to degreased glass substrates using a doctor blade and wascured at 140° C. for 22 minutes. The thickness of the resultingclearcoat was 35 μm. No stress cracks or other surface defects wereobserved. The scratch resistance was outstanding (steel wool scratchtest: rating 1).

Example 16

Preparing an Inventive Dispersion and Producing an Inventive Clearcoaton Plastic

1.0% by weight, based on the dispersion, of the leveling agent Byk® 301from Byk Chemie was added to the inventive dispersion of example 15. Theresulting dispersion was applied pneumatically to the flame-treatedpolycarbonate substrates (Makrolon® from Bayer AG) and cured at 140° C.for 22 minutes.

The coated and uncoated polycarbonate substrates were subjected to thesteel wool scratch test. The polycarbonate substrates coated with theinventive clearcoat showed no visible damage (rating 1), whereas theuncoated polycarbonate substrates were scratched (rating 5).

Example 17

Preparing an Inventive Dispersion and Producing an Inventive Clearcoaton Plastic

Example 16 was repeated but replacing the polycarbonate substrates byflame-treated substrates of polybutylene terephthalate (PBTP). The sameadvantageous results as in example 16 were obtained.

1. An aqueous dispersion, comprising (A) at least one swellable polymerand/or oligomer containing at least one functional group that is atleast one of an anionic functional group, a potentially anionicfunctional group, and/or a nonionic hydrophilic functional groups, (B)surface-modified, cationically stabilized, inorganic nanoparticles of atleast one kind, and (C) at least one amphiphile, wherein the dispersionhas a pH of from 2 to
 7. 2. The aqueous dispersion of claim 1, whereinthe aqueous dispersion has a solids content of up to 60% by weight,based on its total amount.
 3. The aqueous dispersion of claim 1,containing, based on the sum (A)+(B)+(C), from 1 to 30% by weight (A),from 60 to 98% by weight (B), and from 1 to 10% by weight (C).
 4. Theaqueous dispersion of claim 1, wherein the at least one polymer and/oroligomer (A) contains anionic and/or potentially anionic functionalgroups and has, at a pH of from 2 to 7, an electrophoretic mobility≦−0.5 (μm/s)/(V/cm).
 5. The aqueous dispersion of claim 4, wherein theat least one polymer and/or oligomer (A) has at a pH of from 2 to 7, anelectrophoretic mobility ≦−2.0 (μm/s)/(V/cm).
 6. The aqueous dispersionof claim 1, wherein the at least one polymer comprises a copolymerprepared by two-stage or multistage controlled free-radicalcopolymerization in an aqueous or an organic medium wherein (1) in afirst stage (a) at least one olefinically unsaturated monomer (a), and(b) at least one non-(a) olefinically unsaturated monomer of the generalformula (I)R¹R²C═CR³R⁴  (I)  wherein R¹, R², R³, and R⁴ are each independently oneof a hydrogen atom, an unsubstituted alkyl radical, an unsubstitutedcycloalkyl radical, an unsubstituted alkylcycloalkyl radical, anunsubstituted cycloalkylalkyl radical, an unsubstituted aryl radical, anunsubstituted alkylaryl radical, an unsubstituted cycloalkylarylradical, an unsubstituted arylalkyl radical an unsubstitutedarylcycloalkyl radical, a substituted alkyl radical, a substitutedcycloalkyl radical, a substituted alkylcycloalkyl radical, a substitutedcycloalkylalkyl radical, a substituted aryl radical, a substitutedalkylaryl radical, a substituted cycloalkylaryl radical, a substitutedarylalkyl radical, and a substituted arylcycloalkyl radical, with theproviso that at least two of R¹, R², R³, and R⁴ are at least one of anunsubstituted aryl radical, an unsubstituted arylalkyl radical, anunsubstituted arylcycloalkyl radical, a substituted aryl radical, asubstituted arylalkyl radical, and a substituted arylcycloalkyl radical; are copolymerized and then (2) in a second stage at least one furthermonomer (a) is (co)polymerized in the presence of the copolymer formedin the first stage, following the addition of small amounts, or withoutthe addition, of free-radical initiators.
 7. The aqueous dispersion ofclaim 6, wherein the copolymer is prepared by reacting in a first stage(1) at least one monomer (b) with the at least one monomer (a)containing at least one anionic and/or potentially anionic functionalgroup to give a copolymer.
 8. The aqueous dispersion of claim 6 or 7,wherein the copolymer is prepared by reacting in a first stage (1) atleast one monomer (b) with at least one monomer (a) containing at leastone nonionic hydrophilic functional group to give a copolymer.
 9. Theaqueous dispersion of claims 6, wherein the copolymer is prepared byreacting in at least one further stage the copolymer resulting in stage(1) with at least one monomer (a) which contains no anionic functionalgroup, no potentially anionic functional group, and no nonionichydrophilic functional groups.
 10. The aqueous dispersion of claim 1,wherein the potentially anionic functional groups is selected from thegroup consisting of carboxylic acid groups, sulfonic acid groups,phosphonic acid groups, acidic sulfuric ester groups and acidicphosphoric ester groups, and the anionic functional group is selectedfrom the group consisting of carboxylate groups, sulfonate groups,phosphonate groups, sulfate ester groups, and phosphate ester groups.11. The aqueous dispersion of claim 1, wherein the nonionic hydrophilicfunctional group is a polyethylene oxide groups.
 12. The aqueousdispersion of claim 6, wherein the at least one polymer comprises acopolymers which can be prepared in an aqueous medium.
 13. The aqueousdispersion of claim 12, wherein the copolymers is prepared by (1) in afirst stage copolymerizing (a) at least one olefinically unsaturatedmonomer containing at least one functional group that is at least one ofan anionic functional group, a potentially anionic functional group,and/or a nonionic hydrophilic functional group and (b) at least onemonomer different than the olefinically unsaturated monomer (a)  in theaqueous medium and then (2) immediately thereafter in at least onefurther stage subjecting at least one further monomer (a′), differentthan the monomer (a) of stage (1), to block copolymerization with thecopolymer formed in stage (1), wherein the aqueous medium used in stage(1) forms at least a majority of the aqueous medium in which thecopolymer is present in dispersion.
 14. The aqueous dispersion of claim1, wherein the inorganic nanoparticles (B) are selected from the groupconsisting of main group and transition group metals and theircompounds.
 15. The aqueous dispersion of claim 14, wherein the maingroup and transition group metals are selected from the group consistingof metals of main group three, metals of main group four, metals of maingroup five, metals of transition group three, metals of transition groupfour, metals of transition group five, metals of transition group six,metals of group one, metals of group two, and the lanthanides.
 16. Theaqueous dispersion of claim 15, wherein the metals are selected from thegroup consisting of boron, aluminum, gallium, silicon, germanium, tin,arsenic, antimony, silver, zinc, titanium, zirconium, hafnium, vanadium,niobium, tantalum, molybdenum, tungsten, and cerium.
 17. The aqueousdispersion of claim 14, wherein the compounds of the metals are oxides,oxide hydrates, sulfates, or phosphates.
 18. The aqueous dispersion ofclaim 16, wherein the metals and their compounds are selected from thegroup consisting of silver, silicon dioxide, aluminum oxide, aluminumoxide hydrate, titanium dioxide, zirconium oxide, and cerium oxide. 19.The aqueous dispersion of claim 1, wherein the nanoparticles (B) aremodified with at least one compound of the general formula II:[(S-)_(o)-L-]_(m)M(R)_(n)(H)_(p)  (II) in which the indices andvariables have the following meanings: S is a reactive functional group;L is an at least divalent organic linking group; H is a hydrolyzablemonovalent group or a hydrolyzable atom; M is a divalent to hexavalentmain group or transition group metal; R is a monovalent organic radical;o is an integer from 1 to 5; m+n+p is an integer from 2 to 6; p is aninteger from 1 to 6; m and n are zero or an integer from 1 to
 5. 20. Theaqueous dispersion of claim 19, wherein the at least one polymer and/oroligomer (A) contains at least one reactive functional group S isselected from the group consisting of (S1) reactive functional groupswhich contain at least one bond which can be activated with actinicradiation and (S2) reactive functional groups which undergo reactionswith groups of their own kind and/or with complementary reactivefunctional groups.
 21. The aqueous dispersion of claim 20, wherein M isaluminum or silicon.
 22. The aqueous dispersion of claim 1, wherein theamphiphiles (C) are selected from the group consisting of monoalcoholsand aliphatic polyols.
 23. The aqueous dispersion of claim 22, whereinthe monoalcohols are selected from the group consisting of monoalcoholshaving from 3 to 6 carbon atoms in the molecule and the aliphaticpolyols are selected from the group consisting of diols having from 3 to12 carbon atoms in the molecule.
 24. A method comprising applying theaqueous dispersion of claim 1 to a substrate and forming one of acoating for a motor vehicle body or part, a coating for an interiorand/or exterior of a building, a coating for a door, a coating for awindow, a coating for furniture, an industrial coating, a coating forplastics parts, a coating for a coil, a coating for a container, acoating for an electrical component, a coating for white goods, or acoating for hollow glassware.
 25. A method comprising applying theaqueous dispersion of claim 1 to a substrate as a molding or as aself-supporting film.